1. Field of the Invention
The present invention relates to a mobile track working machine arrangement mounted on a track for movement in an operating direction, the track comprising two rails fastened to ties supported on a subgrade by a bed of ballast. The machine arrangement comprises two consecutively arranged, independent track working vehicles, each track working vehicle comprising an elongated machine frame and undercarriages supporting the machine frame on the track. A ballast excavating device is vertically adjustably mounted on the machine frame of a first one of the track working vehicles for excavating the ballast supporting the track whereby the subgrade is exposed, and a conveyor arrangement is mounted on the machine frame of the first track working vehicle for removing the excavated ballast. A device for planing and compacting a protective layer of sand on the exposed subgrade is mounted on the machine frame of a second one of the track working vehicles, and a track lifting device is mounted on each machine frame.
This invention also relates to a method for rehabilitating a ballast bed supporting a track on a subgrade with a track working machine arrangement advancing continuously along the track, which comprises the steps of lifting the track and continuously excavating dirty ballast from under the lifted track to expose the subgrade, discharging sand through the lifted track to lay a protective layer of sand on the subgrade, and planing and condensing the protective layer of sand.
2. Description of the Prior Art
U.S. Pat. No. 4,479,439 discloses a mobile track working machine arrangement for rehabilitating a ballast bed by laying a protective layer of sand between the exposed subgrade and the ballast as the track working machine arrangement continuously advances along the track in an operating direction. This arrangement comprises a vehicle comprising an elongated machine frame supported on the track by undercarriages, and a ballast excavating device is vertically adjustably mounted on the machine frame between two of the undercarriages. A conveyor arrangement is mounted on the machine frame for removing the excavated ballast. Another conveyor arrangement is arranged on the machine frame behind the ballast excavating device in the operating direction for conveying sand and has a discharge end immediately rearwardly of the ballast excavating device for laying a protective layer of sand on the subgrade exposed by the ballast excavating device. A device for planing and compacting the protective layer of sand is mounted on the machine frame immediately rearwardly of the sand discharge end of the other conveyor arrangement. Still another conveyor arrangement is arranged on the machine frame for conveying clean ballast and has a discharge end behind the sand layer planing and compacting device for discharging the clean ballast on the planed and compacted protective sand layer. A track lifting device is mounted on the machine frame centrally between the two undercarriages for lifting the track while the dirty ballast is excavated, the protective sand layer is laid on the exposed subgrade and is planed and compacted, and the clean ballast is discharged on the planed and compacted sand layer.
U.S. Pat. No. 4,357,874 discloses another mobile track working machine arrangement for such a rehabilitation of a track bed by interposing a protective layer of sand between the subgrade and the ballast in a multi-stage operation. This arrangement comprises two consecutively arranged, independent vehicles and each vehicle has an elongated, bridge-like machine frame whose ends are supported on the track by on-track undercarriages. In addition, each machine frame has a vertically adjustable off-track undercarriage adjacent one of the on-track undercarriages. The track bed rehabilitation is initiated by detaching an assembled track section from the track under a first one of the vehicles and lifting the assembled track section off the underlying dirty ballast to create a trackless renewal section. The first vehicle is then advanced to an adjoining track section by suitable operation of the on- and off-track undercarriages supporting the front end of the bridge-like machine frame on the adjoining track section while its rear end is supported on the trackless renewal section by the lowered off-track undercarriage and then by the adjacent on-track undercarriage on the adjoining track section as the off-track undercarriage is retracted. At the same time, the second vehicle is moved over the trackless renewal section in a like manner and a ballast excavating device on the second vehicle excavates the dirty ballast to expose the subgrade. The second vehicle is then moved back again and the first vehicle is returned to the trackless renewal section to lay a protective layer of sand on the exposed subgrade and to lay a ballast bed over the sand layer before the assembled track section is lowered onto the ballast bed. This arrangement is useful primarily for the rehabilitation of short track sections
UIC-Kodex 722 E of the Internationaler Eisenbahnverband (International Railroad Association), of Jan. 1, 1990, also describes a method for rehabilitating a ballast bed. In this method, the dirty ballast is removed by a ballast cleaning machine to expose the subgrade. The excavated ballast is partially deposited on the track shoulder or is loaded onto box cars. The exposed subgrade is then planed and a textile layer may be laid on the planed subgrade. Subsequently, a mixture of gravel and sand is unloaded from box cars and distributed by a ballast planing machine until it has reached the desired depth. Thereupon, a track leveling, lining and tamping machine is used to tamp the gravel-sand mixture under the track ties, whereupon ballast is unloaded from box cars, the track is raised and the track leveling, lining and tamping machine is used to level and line the track and to tamp the ballast under the ties to fix the track in its leveled and lined position. This method requires a considerable number of machines and is, therefore, expensive.
German patent application No. 3,528,152, published Feb. 20, 1986, discloses a machine for rehabilitating a track bed, which comprises a bridge-like machine frame with track lifting devices for lifting the track while an undercutter excavates ballast from under the lifted track to expose the subgrade, a protective layer of gravel or the like is laid on the exposed subgrade, ballast is laid over the protective layer, the ballast is planed and compacted, any gravel and/or ballast on the track ties is swept into adjacent cribs by a rotary brush, and the track is lowered onto the planed and compacted ballast. This patent application is concerned primarily with the mounting of the vertically adjustable and laterally displaceable operating devices of the machine.
Patent No. 159,186 of the German Democratic Republic discloses a ballast cleaning machine carrying a ballast excavating device for excavating ballast under a track to expose the subgrade. A chute extending over the width of the track is mounted on the machine frame and has a front opening receiving sand and a rear opening discharging the sand over the exposed subgrade. A rotary brush is mounted at the front opening of the chute to convey the sand into the opening.